Various examination apparatuses for use in imaging diagnosis (hereafter, referred to as modality apparatuses) are indispensable in modern medical services since they allow examination of internal body in a minimally invasive manner. For example, a nuclear medicine diagnostic apparatus such as a SPECT (Single Photon Emission Computed Tomography) apparatus and a PET (Positron Emission Tomography) apparatus enables diagnosis of functions of organs and tissues. Such a nuclear medicine diagnostic apparatus detects gamma rays radiated from a radioactive medicine selectively incorporated in a living tissue of an object with a detector, and generates a nuclear medicine image from the dose distribution of the detected gamma rays. To be specific, the SPECT apparatus and PET apparatus generate projection data (sinogram data) from the dose distribution of gamma rays detected by the detector, and perform inverse projection processing of the generated projection data, thereby reconstructing a nuclear medicine image (SPECT image and PET image). For example, by using a medicine which accumulates only in cancers, it is possible to examine a metastasis lesion of cancer over the whole body. Moreover, it is also possible to examine the status of blood flow and blood circulation in the brain by using a medicine which accumulates in the brain in accordance with blood flow. However, although a nuclear medicine image has excellent functional information, it is rather lacking in anatomical and morphological information.
In the meantime, an image obtained by an X-ray CT (Computed Tomography) apparatus and an MRI (Magnetic Resonance Imaging) apparatus has high resolution, and provides a plenty of anatomical and morphological information of organs and tissues. Accordingly, by generating a fusion image in which a nuclear medicine image and a CT image or MRI image are fused together (synthesized), it becomes possible to put functional information and anatomical and morphological information together into one image and provide physicians with useful information in imaging diagnosis.
To make high quality diagnosis, it is necessary to appropriately grasp an abnormal area and treatment area from an acquired fusion image. However, reading out an anatomical area from a medical image requires experienced skills and knowledge. Accordingly, as an automated method for identifying and emphasizing a region which is potentially abnormal, various computer assisted detection (CAD) techniques have been developed. For example, a CAD system which specifies an abnormal structure through comparison with a template which has statistical information regarding abnormal areas has been provided. Moreover, as the invention for supporting imaging diagnosis, there are proposed a medical image processing apparatus which specifies anatomical areas by using a segmentation technique etc. and determining a region where abnormality exists and its malignancy, and an image analysis apparatus which determines the positional correlation of images acquired at two different examinations from a structure having a periodicity, such as a spine cord.
In recent years, provision of and study on a technique for representing and constructing anatomical positions of a human body by using a mathematical method have been conducted. The anatomical position means a position of a characteristic local structure of a human body (hereafter, simply referred to as a “local structure”) which plays an important role in understanding medical images, and serves as a mark when mapping a human body in an anatomical fashion. For example, the local structure may be the anterior arch (nodule) of the first cervical vertebra (cervical vertebra I) in the head area, the bifurcation of the trachea in the chest area, and the upper pole of the right kidney in the abdomen area. The position of the local structure (anatomical position) is automatically detected by a general image analysis and pattern recognition technology, etc. from a medical image acquired by a modality apparatus such as an X-ray CT apparatus and an MRI apparatus.
As described above, in imaging diagnosis of nuclear medicine image, identifying an anatomical area in which abnormality is observed, from a fusion image in which a nuclear medicine image and a CT image or MRI image are fused together (synthesized) is generally difficult, and requires experienced skills. Therefore, it takes time to specify anatomical areas where abnormality is observed, which becomes a barrier against early diagnosis. In addition, due to recent improvements in image processing technology, there is a case where the fusion image to be acquired is a three-dimensional image. To specify an anatomical area where abnormality is observed from a three-dimensional fusion image, it is necessary to perform operations such as rotating the image, or continuously observing predetermined sections. Further, it is required to give detailed explanation to the patient on the cause of disease and the content of treatment, and there is need for a display method, etc. for providing explanation to the patient and others in an easy-to-understand manner.
Accordingly, there is need for a medical image display apparatus for easily confirming areas where abnormality is observed on a fusion image by using the above described positions of local structure (anatomical positions).